Generally, a disk-shaped medium such as an optical disk or a magnetic disk is stored in a disk cartridge for dust control or convenient insertion to a recording/reproducing device. Such a disc cartridge has a window to accept insertion of a recording/reproducing head and a turntable for rotation driving of the disk. Further, the disk cartridge has a covering board to open and close the window, which is generally called a shutter. Various optical disks such as a mini disk (MD), a magneto-optical disk, or a DVD, or a flexible disk can be the recording medium having such an arrangement.
As an example of the medium, FIG. 10 shows an arrangement of components included in a disk cartridge of an MD. Further, FIGS. 11A through 11E are schematic diagrams and a cross-sectional view showing the opened state and the closed state of the shutter of the disk cartridge. The disk cartridge 100 adopts a magnetic head and an optical head for recording/reproducing of the disk 103. As shown in FIGS. 11A through 11E, and FIGS. 12A through 12E, the disk cartridge 100 roughly includes a front case 107 and a rear case 108, and stores the disk 103. The front case 107 has an upper window 101 as an insertion hole for a magnetic head, and the rear case 108 has a turntable insertion hole 102c and a lower window 102 for insertion of an optical head. These two windows 101 and 102 can be opened and closed with a shutter 104, and is opened when recording/reproducing is carried out, and is closed when recording/reproducing is not carried out.
Further, when recording/reproducing is carried out, the disk 103 is joined to a turntable of an optical disk device with a magnet due to magnetic force through the lower window 102 via a clamping plate 106 of magnetic material included in the disk 103. The disk 103 joined to the turntable is rotated for driving, and also writing or reading of information signals is performed with the magnetic head or the optical head by making access to the information recording surface of the disk 103 via the upper window 101 and/or the lower window 102.
Note that, the arrangements of cartridges used for the other media stated above do not greatly differ from this cartridge except for the covering before the insertion to a turntable, and the covering method which either uses a shutter and a spring, or uses mechanical covering by a shutter lock.
Further, Japanese Unexamined Patent Publication Tokukaihei 6-131841 (published on May 13, 1994) discloses a disk cartridge having two windows (or may also be called insertion holes) having the same arrangement as above in one surface. In this disk cartridge, in the recording/reproducing, writing and reading of information signals is carried out via the two windows with a recording head and a reproducing head (such as an optical head or a magnetic head) which simultaneously make access to the same signal recording surface. FIGS. 12A through 12E are schematic diagrams and a cross-sectional view showing the opened state and the closed state of the shutter the disk cartridge 200.
Since the component arrangement of the disc cartridge 200 is not greatly differ from the described disc cartridge 100 of an MD, for ease of explanation, materials having the equivalent functions as those of the disk cartridge 100 will be given the same reference symbols, and explanation thereof will be omitted here. As shown in FIGS. 12A through 12E, the disk cartridge 200 has two windows in the same case made of the front case 107 and the rear case 108 for inserting a recording head and a reproducing head. The two windows slide to open in the same directions with the shutter 104. With this arrangement, the disk 103 stored in the disk cartridge 200 can be used for a disk device in which a recording head and reproducing head make access to the same surface at the same time.
Further, the publication above also suggests an example of the disk cartridge having respective shutter 104a and 104b, which are separately opened and closed. In this disk cartridge, when it is used for a disk driving device capable of accepting either of recording/reproducing head to the signal recording surface, the unused window for insertion is closed while the other is opened for accepting a recording/reproducing head to be accessed to the signal recording surface, thus ensuring a superior dust control.
The following will respectively describe two types of the driving device used for recording/reproducing the disk stored in the foregoing disk cartridge.
One is a large-sized driving device for a large disk (for example, a DVD player) capable of recording a large amount of information, and generally fixed in a predetermined place. Another is a small-sized driving device for a small disk (for example, a portable MD player) capable of movable use. These driving devices have different priorities in the performance depending on the purpose of use. For example, a small sized driving device has to be downsized for meeting its purpose of movable use.
Accordingly, in the small sized driving device, the shutter provided in the disk cartridge should not go out of the width of the disk cartridge even in the opened state. The following will discuss the condition of the shutter which does not go out of the width of the disk cartridge even in the opened state with reference to FIG. 11A through 11E, and FIGS. 13A and 13B.
In the cartridge 100 shown in FIGS. 11A through 11E used for such as an MD, a lens center 105a of an optical head 105 is moved on a line a-a′ (a line on the center of the turntable) to carry out recording/reproducing of an optical disk. When the lens center 105a goes out of the line a-a′, the existing optical disk device becomes incapable of position recognition for recording/reproducing. For this reason, as shown in FIGS. 13A and 13B, the disk cartridge 100 has the lower window 102 (insertion hole for the optical head) substantially symmetrical with respect to the centerline (a line a-a′). In this disk cartridge 100, the width of the window W1 is substantially the same as the width of the shutter W2 (note: W1=W2=W) and the lower window has to be the center of the cartridge as thus described in order to meet the requirement of the condition of the shutter 104 which does not go out of the width of the disk cartridge, and therefore the condition is denoted by the following equation;½L/≧½W+W
where L represents the length of opening/closing direction (sliding direction) of the shutter 104.
More specifically, the limitation of the width of the window is about ⅓ of the length L of the cartridge, and also it is ⅓ of the diameter of the disk since it is preferable that the length of the cartridge is substantially the same as the diameter of the disk so as to downsize the disk.
Meanwhile, a major demand for the large-sized driving device used for a large capacity recording medium is high speed information processing for dealing with a large amount of information. Thus, respective driving devices corresponding each diameter have been provided as the large sized driving device. The respective driving devices use optical heads (recording/reproducing head) corresponding to the diameter of the disk so as to realize high speed, high density and stable information processing. Further, for thus realizing high speed, high density and stable information processing, the beam diameter required for the recording/reproducing have to be reduced by bringing the objective lens of the optical head as close as possible to the disk so that the focal distance is reduced. The beam diameter needs to be large to some extent before passing through the objective lens so as to effectively reduce the beam diameter, since it is difficult to adjust the focus of the beam in excessively small diameter. In the small sized driving device whose major demand is downsizing has the limitation of the width of the window in the disk cartridge, and therefore it is impossible to make a large beam diameter. Consequently, high speed information processing is difficult in a small-sized driving device.
Incidentally, in recent years, there has been a new demand of high speed information processing by using a large sized driving device with respect to information recorded on a small disk with a portable small-sized driving device.
To use a small disk in a large-sized driving device, which is normally used for a large disk, the recording/reproducing head in the large-sized driving device needs to be fit to the window (insertion hole for a recording/reproducing head) of the small sized driving device. However, a conventional small disk such as an MD has a window in a width of ⅓ of the width of the disk cartridge. Therefore, when a large-sized driving device is used for the small disk having the small window, as has been described, the particular function of a large-sized driving device, i.e., high speed information processing cannot be expected.
Further, the cartridge 200 disclosed in Japanese Unexamined Patent Publication Tokukaihei 6-131841 does not meet the foregoing requirement either due to the reason above (limitation of the size of the window), though it is adoptable for various recording heads or reproducing heads by having a plurality of windows (insertion hole for recording/reproducing head).